The present invention relates to radio relay transmission systems, and more particularly to a satellite relay transmission system that utilizes a saturated amplifier system to amplify and retransmit synchronously transmitted CDMA signals derived from a ground station.
Satellite communications systems are now well known. In such systems, signals are transmitted from a ground station to a satellite where they are received, amplified, and retransmitted to remotely located receivers. Power consumption, weight, and physical dimensions of the satellite-borne circuitry are of critical importance.
A significant application of satellite communications systems is for mobile communications. In this application, in addition to the critical parameters mentioned above, it is also essential to provide a means to address individual remote users. To this end, CDMA transmissions provide a viable solution. This type of secure transmission may be effected utilizing orthogonal signals or signal groups which can be combined into overlapping beam transmissions. The signals are separable by reason of the characteristics of the orthogonal signals.
In conventional applications, a plurality of orthogonal signals are transmitted to a satellite relay system, where they are combined into the overlapping beam signal using linear amplifiers. While it is well known that linear amplifiers are not the most efficient form of amplifier with respect to power consumption, particularly in digital transmission applications, the need to preserve both phase and amplitude information of the individual CDMA signals has typically required their use.